Articular cartilage is an avascular tissue which lines the ends of the bones and facilitates frictionless movement of the joints, such as the knee joint. Damage to cartilage caused by injury or disease does not heal on its own, and the pathological changes resulting from this damage can be a source of pain and limited mobility to a patient, and can have a significant detrimental impact on the patient's quality of life. Additionally, over time, cartilage lesions are likely to degenerate into osteoarthritis and the need for a total joint replacement.
In some cases, tissue harvesting techniques can be used to treat cartilage lesions and postpone or obviate the need for a joint replacement. These techniques enable a surgeon to purify a unique population of repair cells from the patient's tissues, such as synovial or adipose tissue, and deliver the cells back into the patient's joint to stimulate cartilage repair. The repair cells are harvested arthroscopically from a site local to the defect (i.e. within the joint), and repair cells of a desired size are isolated, for example, by filtering. The isolated cells are typically mixed with a biocompatible “gluing” agent and the mixture of the agent and the harvested cells is then provided to the repair site. The use of autologous tissue is particularly desirable as it substantially reduces the potential for an immunogenic host response and tissue rejection.
Various tissue harvesting techniques for treating cartilage are known in the art. Some examples include mosaicplasty, in which plugs of cartilage and bone are harvested from low weight-bearing regions of the joint and transplanted into the defect; or autologous chondrocyte implantation (ACI), in which cells are isolated and expanded from a cartilage biopsy and re-introduced into the defect in a second procedure. However, some of these techniques, like ACI, involve separate surgical procedures that occur on two different days, which may be weeks apart. Even for single surgery techniques, clinical results suggest that the long-term biochemical and biomechanical properties of the reparative tissue are generally not ideal.